The invention relates to a high-pressure glow discharge lamp having a planar discharge vessel which is sealed in a vacuumtight manner and which encloses a discharge space filled with a gas mixture which forms excimers and whose parallel walls are formed from a dielectric material, the wail surfaces remote from the discharge space being provided with planar electrodes, at least one of said wails with its associated electrode being at least partly transparent to the generated radiation, and the gas mixture comprising at least one of the rare gases Xe, Kr and Ar to form the excimer and at least one of the halogens I.sub.2, Br.sub.2, Cl.sub.2 and F.sub.2.
A dielectrically impeded glow discharge (also called "silent discharge") is generated at a comparatively high gas pressure in a high-pressure glow discharge lamp. In these discharges, a gas filling which emits radiation upon electrical excitation as well as at least one dielectric are present between two planar electrodes which are completely or partly transparent. The electrical supply takes place with an AC voltage. The principle of the discharge is described, for example, in the article by B. Eliasson and U. Kogelschatz, Appl. Phys. B46 (1988) pp. 299-303.
A lamp of the kind described above is known, for example, from EP-A 0 324 953 (see also EP-A 0 254 111, 0 312 732, and 0 371 304). In the present description and claims, a planar discharge vessel which is sealed in a vacuumtight manner is understood to be a discharge vessel which comprises at least two substantially parallel walls, whose dimensions are large in comparison with the interspacing between these walls, and a side wail which seals off the assembly in a vacuumtight manner, while the walls may be plane-parallel or, alternatively, coaxial and a striking distance (d) is determined by the distance between the inner surfaces of the walls.
A dielectric, i.e. an electrically non-conductive material is used for the walls of the discharge vessel. At least one of the parallel walls is transparent to the generated suitable materials for the transparent wall include for example, glass, quartz, which is also transparent to UV, or the fluorides of magnesium or calcium which are transparent to very short-wave radiations. The dielectrics mentioned are in general resistant to breakdown and chemically resistant to the gas filling. The planar electrodes may be made of metal, for example, metal plating or metal layers. Transparent electrodes may be constructed as mesh or grid electrodes, for example, wire meshes or gold grids, or alternatively as transparent gold layers (5-10 nm), or electrically conducting layers such as indium oxide or tin oxide.
The invention has for its object to provide a high-pressure glow discharge lamp which has a high radiant efficacy, and, in addition, to render possible homogeneously emitting planar radiation sources having a large surface area and a high radiant efficacy.